Improved Model-Free Adaptive Control of Pneumatic Gravity Compensation System

Abstract

A pneumatic gravity compensation system is typically nonlinear in behavior. It is difficult to establish an accurate mathematical model for it, and it is particularly difficult to realize high-precision pressure control. A pneumatic gravity compensation system driven by a frictionless cylinder is built. Considering that the traditional model-free adaptive control is slow for pseudo-gradient identification, an improved model-free adaptive control is proposed to predict the changes in the pseudo gradient and accelerate the process of pseudo gradient identification. The static and dynamic gravity compensation of the pneumatic gravity compensation system is realized. Finally, the experimental results show that the steady-error of step response of the improved model-free adaptive controller is less than 200 Pa, and the rise time is approximately 13 seconds. The sinusoidal tracking error (0.04 Hz) is approximately 1.94 KPa.